Microneedle Patches:Design for SuperiorDrug Delivery

By Luis Tissone, Director of Life Sciences,
Trelleborg Sealing Solutions

We are experiencing a tremendous upsurge in the medications delivered
transdermally. This drug delivery
system provides are several benefits
over traditional methods, including
systemic delivery of the medication
to the patient. In particular, microneedle patches and other products have great potential for vaccine
delivery. This article will explore the
material components that go into the
manufacture of microneedle-based
delivery systems as they are crucial
for ensuring the highest quality and
performance.

Optimum Material for Optimum
Results

There are four types of microneedles
currently on the market:

1. Hollow microneedle: requires a liquid drug formulation to be infused
through the bores.

2. Solid microneedle: punctures holes
in the skin where a patch can then
be applied.

3. Dissolving microneedle: coated
with the drug.

4. Polymer microneedles: made from
special polymers offering dissolving, non-dissolving or hydro-gel-forming options.

In each case, these microneedlepatch types offer an excellent deliveryroute to enhance the vaccination’seffectiveness. This is due to the factthat microneedles possess the abilityto target the rich network of immu-nologic antigen-presenting cells in thedermis and epidermis layers under theskin. Many new studies show that mi-croneedle use for vaccination deliveryreveals either comparable or greaterimmunogenicity, a stronger level ofstability, and more advantageous dosesparing as compared to the traditionalintramuscular routes.

Advanced technologies are coming
into play in enhancing microneedle
components during the design process. For example, product developers
and research institutes are looking
at the use of liquid silicone rubber
(LSR) technology and two-compo-nent injection technology to enhance
the performance of their transdermal
delivery systems.

Silicone - and LSR in particular - is
becoming an increasingly attractive
choice of polymer due to a number of
advantages. Silicone is well regarded
for its favorable haptic properties and
proven to generally not cause skin
irritation. In addition, silicone provides
biocompatibility and compliance with
relevant industry regulations. Most
importantly, LSR offers fast, essentially
unlimited processing possibilities for
the most complex high-precision technical components in large volumes.

LSR technology is particularly
effective when custom solutions are
needed, due to its adaptability. It is
also well suited when multiple materials or layers of materials need to be
combined into a composite structure.

For surface enhancements and surface
texturing, LSR provides the intended
absorption of medicine through the
skin. Lastly, LSR works extremely
well when the most complex, thin,
and/or tiny features are needed, such
as a protective element or carrier as
part of a microneedle patch. It provides the highest component precision
and consistency of quality.

Advancements in drug delivery
systems will be the result of access to
newly developed materials, emerging
technological delivery methods and
advances in manufacturing capabilities. LSR technology can deliver
smaller, more robust and stronger
polymers to provide more stability,
wear and usage.

Microneedles and Microfabrication
Manufacturing

Microneedles consist of a plurality of
micro-projections, generally ranging
from 25–2000µm in height, of different
shapes, which are attached to a base
support. Microfabrication manufacturing technology can help in delivering
innovative microneedle designs. There
are numerous configurations that can
compose a microneedle patch. The
flexibility of LSR can assist in achieving those configurations regardless of
complexity.

The first microneedle devices were
fabricated from silicone but many other materials have also been used in its
fabrication like stainless steel, dextrin,
glass, ceramic, maltose, galactose, and
various polymers.